Me: “I’ve decided to start eating healthier, so I’m going to cut down on junk food and eat more protein.”
Friend: “I wouldn’t do that.”
Me: “Why not?”
Friend: “I’ve heard protein is really bad for your kidneys.”
Me: “…. F**k.”
Is there anything more rage-inducing than trying to get healthier, only to be told that even the things you thought were healthy are in fact still not good enough?
Aside from maybe being stuck in a lift with a Juice Plus salesman, I can’t think of one.
It’s enough to make a person think, “Why bother?”, and just go right back to square one again, and that’s exactly what it tends to do.
So today I want to help you answer one of the biggest, most popular beliefs in the fitness industry — is a high protein diet bad for your kidneys?
Strap in, and get ready to make some self-appointed “experts” at your workplace rather unhappy…
The theory behind a high protein diet being bad for your kidneys makes sense, at least on the surface.
A 1988 study first discovered that increased protein intake led to a higher glomerular filtration rate, which is used as a marker for waste filtration in the kidneys. It was initially believed that this showed our kidneys are being placed under increased stress when we consume a diet rich in protein. (1)
However, more recent studies have long debunked this theory.
A 2003 study published by researchers at Harvard Medical School, Boston, found that a high protein diet did not place undue stress on the kidneys, nor did it raise glomerular filtration rate in women with normal renal function.
However, they did notice some negative effects in a subgroup of study participants who had mild renal insufficiency. (2)
The researchers concluded:
“High protein intake was not associated with renal function decline in women with normal renal function. However, high total protein intake, particularly high intake of nondairy animal protein, may accelerate renal function decline in women with mild renal insufficiency.”
This time around, researchers from Belgium looked at the effects of a high protein diet on the kidneys of bodybuilders and well-trained athletes. They tested the participants with a protein intake of up to 2.8kg per kg of body weight (224g protein for an 80kg/176lb person) and concluded that it had not impaired renal function in any of the athletes involved. (3)
Using well-trained men as the study participants, they followed their regular diet for a period of six months followed by a higher protein diet for six months, giving the researchers an entire year of results to work with.
During the six months of their own diet, the participants consumed an average of 0.69g protein per kg (55g for an 80kg person). This was the ramped up significantly during the remaining six months, but the researchers again did not discover any negative effects on kidney function in any of the participants. (4)
Contrary to what many people believe, there isn’t a shred of evidence to suggest that consuming a high protein diet will cause damage to your kidneys.
And any studies which do suggest a link, also make it clear that participants had pre-existing kidney disease or other kidney disorders.
But feat not.
I’d advise you not to put too much stock in what the media report, because they often sensationalize the results of studies in order to create headlines. After all, this is the same media who once told you drinking a glass of red wine is as good as an hour of exercise. And that fish oil causes prostate cancer.
Instead, listen to the researchers themselves.
Here’s what nutrition expert Mark Gilbert had to say:
“There is no evidence to support claims of high protein diets causing kidney damage, but that doesn’t stop this myth from remaining very popular!
In fact, a dietitian recently emailed me and claimed that protein may have those dangerous side effects. However, when I asked her to support her stance with scientific facts, she could not provide any evidence whatsoever that this was the case.”
Muscle & Fitness magazine senior science editor Jim Stoppani, who follows a very high protein diet himself, also backs this up:
“Sadly, the media and some ‘experts’ have misinformed the general public that protein is dangerous for the kidneys.
Yes, if you have pre-existing kidney damage, a high protein diet may be less than ideal for your body. But for the rest of us, our kidneys were designed for that very function, and so they don’t become overburdened.”
So, there you have it.
Unless you have pre-existing kidney damage there is absolutely no scientific evidence at all to support any claims that a high protein diet will cause damage to your kidneys.
If any ever exists in future, I will tell you otherwise by updating this article with it.